The primary structure of human pepsin and gastricsin is to be studied. Previous work has revealed the NH2-terminus structure of about 25 residues each. Future work will aim at the solving of the complete sequences. Other work under this project includes the study of the mechanisms of intramolecular activation of pepsinogen and the mode of inhibition of pepstatin on pepsin and other acid proteases. Bibliographic references: Sepulveda, P., Jackson, K. and Tang, J. (1975) Biochemical and Biophysical Research Communications 63, 1106; Sanny, C.G., Hartsuck, J.A. and Tang, J. (1975) J. Biol. Chem. 250, 2635.